Hunters after deer, bear, and other large animals have to select their positions carefully with respect to wind direction. The animals have an acute sense of smell, and any whiff of human scent will alert them to the danger. Usually, the hunter will select a position of concealment with a good view of a known trail, and which is down-wind at the moment from where he expects the animals to appear. When there is a brisk breeze, this usually presents no problem. In calm air, however, imperceptible changes in local air movement can carry the telltale scent with them. A sudden reversal in such air movement can make it necessary to change position quickly.
When air is moving at only one or two feet per second, it becomes very difficult to detect its direction accurately. Sophisticated draft-detection instruments are expensive and cumbersome. Smoke from a cigarette is itself a giveaway. The present invention provides a very inexpensive and remarkably sensitive detector for the direction of air movement.